First Lasing at ELBE
We are pleased to announce the first lasing of the infrared FEL at the Radiation Source ELBE on 07 May. Thus, an important milestone is accomplished to the completion of the radiation source ELBE and the European infrared user's lab FELBE.
The superconducting electron accelerator supplied a 16,1 MeV beam. The beam was macropulsed with 0.4ms pulse length and 5Hz repetition rate. The current in the macropulse was 600 µA. The Undulator (λ=27,3 mm) was operated at a gap of 13.8 mm (Krms=0.7). Initially, spontaneous radiation of approximately 10 µW was observed. After the adjustment of both mirrors in the optical cavity and the cavity length lasing started with a wavelength of 19.8 µm. The spectral width at 10 µm cavity length detuning was 1.3% (fwhm).
Initially, 0.3 W optical power could be outcoupled during the macropulse. After further optimization 3 W were reached with a 1% outcoupling through a 2 mm hole in one of the mirrors. The Laser saturates approximately 50 µs after the macropulse start. During the exponential rise the intensity increases in less than 5 µs by one order of magnitude. This indicates more than 4% roundtrip gain minus losses.
|The signal of the infrared detector is shown in two different scales in channel 2 and 3 on the scope. By comparison one can estimate the rise time of the signal.|
So far, all these parameters correspond to the calculations and the expectations. After entire commissioning ELBE should supply IR radiation from 5-25 µm up to 10 W. In six specially equipped user labs experiments for semiconductor physics, biology and radiochemistry are planned . The user's Lab should go on line in autumn, 2004. With the installation of the second accelerator cryomodule and a planned second optical resonator for longer wavelengths, the spectral range will be extended to 3-150 µm at up to 100 W power.